We examined biomicroscopically the vitreous and retinal conditions of 902 consecutive symptomatic eyes (785 patients) to ascertain the relationship between floaters, light flashes, or both, and complications of posterior vitreous detachment. Of 785 patients, 785 symptomatic eyes were divided as follows: group 1, 342 eyes with floaters alone; group 2, 240 eyes with floaters and light flashes; and group 3, 203 eyes with light flashes alone. We also studied 636 asymptomatic fellow eyes. The prevalence of posterior vitreous detachment was significantly higher in groups 1 (138 of 342, 40%), 2 (214 of 240, 89%), and 3 (137 of 203, 67%) than in the asymptomatic eyes (127 of 636, 20%), in group 2 than in groups 1 and 3, and in group 3 than in group 1 (P = .01). The prevalence of retinal breaks in eyes with posterior vitreous detachment was 5% (seven of 138), 13% (27 of 214), 12% (16 of 137), and 4% (five of 127) in groups 1, 2, 3, and the asymptomatic eyes, respectively; the prevalence was significantly higher in groups 2 and 3 than in asymptomatic eyes (P = .02 and P = .04) and group 1 (P = .04 and P = .05). The prevalence of vitreous hemorrhage in eyes with retinal breaks was 71% (five of seven), 70% (19 of 27), and 6% (one of 16) in groups 1, 2, and 3, respectively. Of 117 patients with bilateral symptoms, 105 (90%) had the same symptoms and 104 (89%) had the same vitreoretinal relationship bilaterally.(ABSTRACT TRUNCATED AT 250 WORDS)